The National Association
of Biology Teachers recognizes the importance of laboratory activities
using human body samples and has developed minimum safety guidelines to
minimize the risk of transmitting serious disease. ("The Use of Human
Body Fluids and Tissue Products in Biology," News & Views,
June 1996.) These are summarized below:

Only collect samples
from students under your direct supervision.

Do not use samples
brought from home or obtained from an unknown source.

Do not collect
samples from students who are obviously ill or are known to have a serious
communicable disease.

Have students
wear proper safety apparel: latex or plastic gloves, safety glasses
or goggles, and lab coat or apron.

Supernatants and
samples may be disposed of in public sewers (down lab drains).

Have students
wash their hands at the end of the lab period.

Do not store samples
in a refrigerator or freezer used for food.

The mouthwash method
of DNA isolation does generate liquid waste; however, the risk of spreading
an infectious agent is much less likely than from natural atomizing processes,
such as coughing or sneezing. Several elements further minimize any risk
of spreading an infectious agent that might be present in mouthwash samples:

Each experimenter
works only with his or her sample.

The sample is
sterilized during a 10-minute boiling step.

There is no culturing
of the samples that might allow growth of pathogens.

Samples and plasticware
are discarded after the experiment.

Consent
and Confidentiality

Student
particpation in this experiment raises real-life questions about the use
of personal genetic data:

What is my DNA
sample being used for?

Does my DNA type
tell me anything about my life or health?

Can my data be
linked personally to me?

There
is concensus that a human DNA sample should be obtained only with the
willing consent of a donor, who understands the purpose for which it is
being collected. Thus, the experiments should be explained ahead of time
and students given the option to refrain from participating. (Some teachers
may wish to have parents sign a consent from, such as those filled out
for a field trip.) There is also consensus that a DNA sample be used only
for the express purpose for which it is collected. Thus, student DNA samples
should be thrown away after completing the experiments in this unit. (In
fact, the cheek cell samples are not stable enough for long term storage.)

The
Alu PV92 insertion and mt control region polymorphisms used in
these experiments were specifically selected because they are phenotypically
neutral. Neither locus encodes a protein, nor has any known relationship
to disease states, sex determination, or any other phenotype.

Even
though there is no chance of disclosing phenotypic information about the
experimenters, all student polymorphism data stored at our Allele Server
and Sequence Server sites are anonymous. Online submission forms
identify students only by number and have no entry fields for personal
identifiers. We recommend that each student select a four-digit personal
identification number (PIN) and label their experiment with this number.
Under this system, there is no chance that a student can ever be linked
to his/her sample in the database. Alternately, students can be assigned
a sequential number, with no permanent key maintained by the teacher.

Family
Relationships

All
polymorphisms are inherited in a Mendelian fashion and can give indications
about family relationships. The PV92 polymorphism has an inherently low
information content – usually there are at least several parental genotypes
that could account for an observed student genotype. On the other hand,
mitochondrial (mt) DNA genotypes are explicit records of maternal inheritance
that are usually unique to each family. Since mt DNA is inherited exclusively
from the mother, there is no chance of showing nonpaternity, which is
the most frequent problem uncovered by DNA testing. However, inconsistent
mt DNA types between siblings and/or mother could suggest adoptive situations.

To
avoid the possibility of discovering inconsistent mt DNA inheritance,
we recommend that you do not generate genotypes from family members. However,
in a formal sense, a single data set – even for mt sequence – cannot definitively
prove or disprove relatedness for several reasons:

Student samples
can be easily mixed up, by mislabeling or misloading, at any point in
the multi-step procedure – DNA isolation, PCR reaction, and gel electrophoresis.
A forensic laboratory would use approved methods for maintaining "chain
of custody" and for tracking samples, which insure that a specific
result is from a specific sample. However, we do not recommend instituting
rigorous controls to insure sample identity. In an educational setting,
"limited sloppiness" provides a safety valve for inconsistent
results.

A single "read"
of mt DNA sequence is not definitive. Sequence errors do occur during
amplification, sequencing, and "base calling" by the sequencing
software. Finished DNA sequences submitted to DNA databanks have typically
been resequenced 2-8 times to clarify any discrepancies in single reads.
At a minimum, a reverse read of the complmentary DNA strand would be
required for any definitive determination.

New mutations
and heteroplasmy occasionally occur in mt DNA lineages. A new mutation
may occur in one family member, resulting in a different nucleotide
at that position. A new mutation may also lead to a situation know as
heteroplasmy – when cells harbor two populations of mitochondria, each
with a different nucleotide at a particular position.